This application claims the priority of German patent 198 23 797.9-24, filed May 28, 1998, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a device for continuous casting of workpieces, using a melting crucible, a filling device, and a forming tool provided with a temperature control system. The invention also relates to a method for continuous casting of workpieces with a melt being fed to a melting crucible, and with the melt entering a forming tool provided with a temperature control system through a filling device.
A platemold for producing strands of steel is known from German patent document DE 195 29931 C1, in which the broad side walls have at least three adjacent, mutually independent cooling sections. As a result it should be possible to make a differentiated statement about the partial heat flux across the width of the mold.
German patent document DE 32 04 339 A1 describes a continuous casting mold for casting support blanks that is provided with coolant lines.
Another device as well as a corresponding method are known from German patent document DE-OS 26 50 016. In this method, referred to as extrusion, an endless strand is pulled out as a workpiece from a liquid metal in a forming tool, referred to in this case as an extrusion die.
A method for manufacturing pipes, wires, etc. is known from German patent document DE-PS 429 217 which links the familiar centrifugal casting method with the likewise known extrusion molding method.
Moreover, German patent document DE 31 50 684 C2 describes a semi-continuous continuous casting process for metals with a strand to be pulled out and upward. With the very complex method described in this document, assurance is to be provided that strands of excellent quality and free of segregation can be manufactured from even complex alloys with a high production efficiency.
It is disadvantageously no t possible with this method and device to manufacture workpieces with complicated cross sections that have different thicknesses, in particular by continuous casting.
The continuous casting and extrusion molding methods are also known from the general prior art in addition to the documents cited above. In order to manufacture any profiles, even those that can be partially very complex reflecting their applications, a semifinished product is usually manufactured by continuous casting and then given its final shape by extrusion molding.
The high manufacturing expense and the associated high costs of this process and the devices used for the purpose however are very disadvantageous.
Hence, an object of the present invention is to provide a device and a method for continuous casting with which workpieces with complex cross, sections, with different thicknesses or wall thicknesses that change over the cross section, can be manufactured.
This and other objects have been achieved according to the present invention by providing a device for continuous casting of a workpiece, comprising: a melting crucible; a filling device; and a forming tool provided with a temperature control system, the temperature control system of the forming tool being designed such that areas of a workpiece to be manufactured that have a greater wall thickness can be cooled to a greater degree and areas of the workpiece to be manufactured that have a lesser wall thickness can be cooled to a lesser degree and/or heated such that a solid-liquid interface of the workpiece lies in a plane that is at least approximately perpendicular to the vertical axis of workpiece.
This and other objects have also been achieved according to the present invention by providing a method for continuous casting of a workpiece defining at least one interior recess, the workpiece having a varying wall thickness, comprising: feeding a melt to a forming tool provided with a temperature control system; and cooling areas of the workpiece to be manufactured having a greater wall thickness to a greater degree in the forming tool than areas of the workpiece to be manufactured having a lesser wall thickness.
This and other objects have also been achieved according to the present invention by providing a forming tool for a continuous casting machine, comprising: a forming tool defining an opening corresponding to a cross-section of a workpiece to be cast, the opening including wider openings corresponding to areas of the workpiece to be cast having a greater wall thickness and narrower openings corresponding to areas of the workpiece to be cast having a lesser wall thickness; a temperature control system provided in the forming tool, the temperature control system being designed to cool the forming tool to a greater degree adjacent the wider openings, the temperature control system being designed to at least one of (a) cool the forming tool to a lesser degree, and (b) heat the forming tool, adjacent the narrower openings.
This and other objects have also been achieved according to the present invention by providing a method of controlling the solidification of a melt in a continuous casting machine having a forming tool defining an opening corresponding to a cross-section of a workpiece to be cast, the opening including wider openings corresponding to areas of the workpiece to be cast having a greater wall thickness and narrower openings corresponding to areas of the workpiece to be cast having a lesser wall thickness, the method comprising: cooling the forming tool to a greater degree adjacent the wider openings; and at least one of (a) cooling the forming tool to a lesser degree, and (b) heating the forming tool, adjacent the narrower openings.
This and other objects have also been achieved according to the present invention by providing a system for controlling the solidification of a melt in a continuous casting machine having a forming tool defining an opening corresponding to a cross-section of a workpiece to be cast, the opening including wider openings corresponding to areas of the workpiece to be cast having a greater wall thickness and narrower openings corresponding to areas of the workpiece to be cast having a lesser wall thickness, the system comprising: means for cooling the forming tool to a greater degree adjacent the wider openings; and means for: at least one of (a) cooling the forming tool to a lesser degree, and (b) heating the forming tool, adjacent the narrower openings.
With the design of the temperature control system of the forming tool according to the invention, areas of the workpiece to be manufactured with a greater wall thickness can be cooled to a greater degree and areas with lesser wall thicknesses can be cooled to a lesser degree, or even heated. As a result, it is possible to manufacture workpieces with any cross section, especially with a complex cross section, by continuous casting, since the solid-liquid interface, in other words the area in which the melt changes into the finished workpiece, despite the different wall thicknesses, is distributed uniformly over the cross section. One could even speak of a symmetrical course of the solid-liquid interface over the cross section, in which the average of the areas that have last hardened is located like a resultant of forces at the center of the workpiece. Advantageously, the cast strand now emerges in a straight line from the forming tool.
The previous problem that areas with a greater wall thickness take longer to set than areas with a lesser wall thickness and therefore a very considerable delay would occur at the strand emerging from the mold therefore no longer applies.
The method according to the invention makes it possible to eliminate the extrusion that was previously required in addition to continuous casting to make workpieces with more complex cross sections.
According to certain preferred embodiments, the temperature-control system of the forming tool has coolant lines and optionally also heating lines.
According to certain preferred embodiments, a greater concentration of coolant lines is provided in areas of the forming tool proximate portions of the workpiece to be manufactured that have a greater wall thickness than in areas of the workpiece to be manufactured with a lesser wall thickness.
According to certain preferred embodiments, coolant lines having a larger diameter are provided in areas of the forming tool proximate portions of the workpiece to be manufactured that have a greater wall thickness than in areas of the workpiece to be manufactured with a lesser wall thickness.
By adjusting the number or the size (e.g., the diameter) of the coolant lines or the heating lines, a simple change can be made to the design of the temperature-control system according to the invention.
According to certain preferred embodiments, the forming tool is designed with a greater height in areas with a greater wall thickness of the workpiece to be manufactured than in areas with a lesser wall thickness of the workpiece to be manufactured.
According to certain preferred embodiments, adjacent areas of the forming tool with a lesser height, an in-flow area is provided in the filling device, with the height of this area corresponding to the difference between the height of higher areas of the forming,tool,and the height of flatter areas of the forming tool.
The reduced height or length of the forming tool in workpiece areas with reduced wall thicknesses produces a reduced effective height of the temperature control system, which therefore produces a reduced cooling effect in the areas of the workpiece to be manufactured that have a reduced wall thickness.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.